1. Field of the Invention
This invention relates to a marine engine, and more particularly to a cooling system employed in a marine engine.
2. Description of the Related Art
Personal watercraft, like other applications that use internal combustion engines as prime movers, are experiencing considerable public and governmental pressure to improve not only their performance, but also their exhaust emissions level. For example, due to the emissions generated by two-stroke powered watercraft, certain recreational areas have banned the operation of such watercrafts. These bans have decreased the popularity of personal watercraft, and have caused manufacturers of these types of watercraft to consider fuel injected engines to power their watercraft and/or other means to reduce emission levels.
Fuel injected engines are known to provide a significantly enhanced performance, power output, and emissions as compared to carburated engines. All even more significant improvement is achieved through direct cylinder injection. Direct cylinder injection may be accompanied by stratification or lean burning operation to further fuel economy and emission control.
The benefits of fuel injection are further enhanced through the control of the engine block temperature during operation. For example, it has been known to employ a thermostat within the cooling system of a watercraft so as to control the flow of coolant through the cooling system of a watercraft.